In sheet processing devices which manufacture a product from a sheet-shaped material (sheet-shaped workpiece, hereinafter, simply referred to as a sheet) such as a paper converting machine which manufactures a paper product from a sheet-shaped paper, there is a sheet processing device including a sheet feeder which supplies sheet to a upstream portion. For example, in a case of a carton-forming machine which is a representative paper converting machine, a sheet feeding section, a printing section, a creasing and slotting section, a die-cut section, a folding section, and a counter-ejector section are provided in this order from an upstream side, a corrugated fiberboard (simply referred to as sheet) which is supplied from the sheet feeding section and is a sheet-shaped workpiece is processed so as to manufacture a corrugated box.
A corrugated fiberboard supply device corresponding to the sheet feeder is installed in the sheet feeding section of the carton-forming machine. In the corrugated fiberboard supply device, in general, a wheel (also referred to as a feeding roll or a paper supply roll) and a grate (a lattice-shaped support plate) are used. That is, the wheel and the grate is installed in a front (a direction in which paper is supplied) portion of a paper supply table on which stacked sheet is placed, and a front guide is installed in front of the wheel and grate such that the lower edge is disposed so as to be higher by approximately one sheet than the upper surface of the paper supply table. In addition, feed rolls paired vertically are installed in front of the front guide to be separated from each other by a thickness of approximately one sheet.
The wheel is disposed such that the upper end is positioned so as to be slightly higher than the upper surface of the paper supply table. The wheel repeats operations which are intermittently driven, start to rotate from a stopped state, are accelerated to reach a paper passing speed, that is, the same circumferential speed as a circumferential speed of the feed roll, and thereafter, are decelerated so as to be stopped. The grate is formed in a lattice shape, and the wheel is disposed in a gap formed therein. The upper surface of the grate is raised and lowered synchronously with the operation of the wheel between a position above the upper edge of the wheel and a position below the upper edge, cause the lowermost sheet to come into contact with the upper edge of the wheel at the time of lowering, and separates the lowermost sheet from the upper edge of the wheel at the time of raising.
In the corrugated fiberboard supply device, a paper supply is performed in cooperation with the rotation of the wheel and raising and lowering operations of the grate. That is, first, the grate is lowered, and the lowermost sheet comes into contact with the wheel. In this state, the wheel starts rotation, is accelerated to the paper passing speed, and delivers the lowermost sheet to the feed roll. Here, the grate is raised such that the next sheet does not come into contact with the wheel, and the next sheet is prevented from being supplied. During this time, the wheel is decelerated to stop the rotation. The paper is continuously supplied by repeating this operation.
Basically, the paper supply by the corrugated fiberboard supply device is performed so as to be interlocked with a main drive system, and for example, if a printing cylinder of the printing section rotates once, the paper supply is performed once. However, for example, in a case where a corrugated fiberboard which is long in a transport direction is processed, a skip-feed may be performed in which the paper supply is performed once per two rotations of the printing cylinder of the printing section. This skip-feed can be performed by changing the raising and lowering operations of the grate.
As a technology which can change the raising and lowering operations of the grate, for example, PTL 1 discloses that a single-mode cam which raises the grate once per one period of a machine and a multiple-mode cam which raises the grate a plurality of times per one period of a machine are coaxially provided, and an air cylinder is provided separately from the cams. In this technology, even when the single-mode cam is positioned at a position (that is, a position which lowers the grate) which does not raise the grate, it is possible to raise the grate by the air cylinder and to perform the skip-feed.
Moreover, PTLs 2 to 6 disclose configurations in which stationary cam and a movable cam are coaxially provided and the grate is raised and lowered at the time defined by a combination of the stationary cam and the movable cam so as to change raising and lowering operations of the grate, and it is possible to perform the skip-feed by lengthening a raising period of the grate by adjusting a phase of the movable cam.